Annual summer bleaching of a multi-species coral community in backreef pools of American Samoa: a window on the future?

Abstract

The prevalence of bleaching was recorded in staghorn thickets of two back reef pools on a biweekly basis during the October to June bleaching season, and monthly basis for the rest of the year at Tutuila, American Samoa. Recording began in late 2003 and has continued since, and used a rapid visual estimation procedure. Three species of staghorns (Acropora spp.) in both pools bleached every Austral summer for five years. Reports of reef slope bleaching events in 2002 and 2003 imply that they bleached in those years as well. Thus, these corals have bleached for at least five summers and likely seven summers or more in a row. Other, less common species of Acropora and Millepora were observed to bleach as well. The bleaching displayed patterns consistent with the view that both temperature and irradiance are involved in producing the bleaching. The term “photothermal bleaching” was applied to this type of bleaching. This appears to be the first annual multi-species summer bleaching event reported.